Breaking the Gastight Boundary of the CO2 Room
The fixed CO2 room is on the boat deck, bounded by steel bulkheads; the aft bulkhead separates it from a store. The boundary is required to be gastight. The carpenter is asked to cut a 600 by 600 mm opening in the aft bulkhead and fit a plywood access panel so that an engineer can reach a cable gland, and to run a 50 mm timber cable duct through the top of the bulkhead above the CO2 room door. The room's steel door has a 20 mm gap at the bottom and its mechanical ventilator flap is jammed open. The CO2 system's pre-discharge alarm and delay are functional, and the room contains the manifold and 12 cylinders. The chief engineer says the access panel is only temporary and will be screwed shut with a rubber gasket.
1. Which elements compromise the gastight boundary, and why does gastightness matter beyond fire?
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The compromised elements are:
- The proposed 600 by 600 mm plywood panel. Plywood is combustible, dimensionally unstable and cannot be made gastight by screwing it down onto a rubber gasket. Screws do not give uniform compression, and the panel will leak at the joints and around the cut edges.
- The 50 mm timber cable duct through the bulkhead above the door. It is combustible, creates an unprotected opening and cannot be sealed to the standard of a steel boundary. Cable penetrations need approved gastight transits, not a timber sleeve.
- The 20 mm gap at the bottom of the door. A door gap of that size defeats the boundary and also defeats smoke containment. The door should close onto a gasket or seal.
- The jammed-open ventilator flap. The room must be capable of being closed tight; a flap that cannot be shut means the boundary is permanently open.
Gastightness matters because a CO2 discharge creates an oxygen-deficient, lethal atmosphere. If the boundary leaks, CO2 can pass into the adjacent store or accommodation, where people may be working without any alarm or warning. It also matters for fire containment and for the safe entry and ventilation of the space. A 'temporary' plywood panel is therefore not a temporary issue; it is a life-safety defect for as long as it is fitted.
2. State the acceptable way to achieve the engineer's access without a plywood panel, and the testing and acceptance you would require.
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Acceptable access: the engineer's need is to reach a cable gland, so the first option is to relocate the gland or route the cable outside the CO2 room, eliminating the need for an opening. If access into the room is genuinely required, the opening should be a steel access panel or a properly designed steel door with a gasketed seat and dog clamps, fitted to the approved boundary standard. The frame should be continuously welded or bolted with a gasket, and the panel should be marked and secured so it cannot be left open. Cable penetrations should use approved gastight cable transits, not timber ducts.
Other repairs: renew the door gasket and bottom seal, and repair or renew the ventilator so that it closes tightly and can be operated from outside, with a clear open/closed indicator.
Testing and acceptance:
- With the door and ventilator closed, carry out a room integrity or air-tightness test, or a smoke test, to demonstrate the boundary holds.
- Have the classification surveyor attend and confirm the boundary and the CO2 system's readiness; re-commission the system and confirm the pre-discharge alarm and delay still function.
- Record the test, the materials used and the surveyor's acceptance in the CO2 system file, and update the fire plan and entry procedures.
3. What immediate actions would you take if the vessel must sail before the boundary is restored?
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- Do not accept the plywood panel or the timber duct as a sailing arrangement. They leave a lethal-atmosphere risk in an adjacent space and undermine the CO2 system's effectiveness.
- Make a safe temporary closure using a steel blank of adequate thickness, a proper gasket and dog clamps or bolted fixings, and seal any cable penetration with an approved transit. Repair the door gasket and secure the ventilator closed. This is a genuine temporary repair, not a combustible patch.
- Inform the master, the company and the classification society/flag in writing. If the boundary cannot be restored, the vessel should not sail with the CO2 system as the sole fixed firefighting provision for the machinery spaces without formal acceptance of the deficiency and compensating measures.
- Control access: keep the CO2 room locked, post warning notices, prohibit entry except for authorized persons, and brief the crew on the condition and on the pre-discharge alarm.
- Record everything: defect report, temporary repair, test results, correspondence and a dated deadline for permanent restoration. The chief engineer's assurance that the panel is 'only temporary' is not a substitute for a tested boundary.